tlbilxlpid -> error: invalid instruction

[nickdesaulniers]

via https://lore.kernel.org/llvm/202307211945.TSPcyOhh-lkp@intel.com/

it looks like:

void foo(void) {
    asm volatile("tlbilxlpid");
}

produces:

<source>:2:18: error: invalid instruction
    asm volatile("tlbilxlpid");
                 ^
<inline asm>:1:2: note: instantiated into assembly here
        tlbilxlpid
        ^~~~~~~~~~

for --target=powerpc-linux-gnu. I wonder if clang is missing support for this instruction (or perhaps it's an alias to something that clang does understand).

cc @nemanjai @nemanja-ibm

[llvmbot]

@llvm/issue-subscribers-backend-powerpc

[MaskRay]

It looks like tlbilxlpid is an alias for tlbilx 0, 0, 0, which is present in Power ISA v2.07, but not in Power ISA v3.x.

[nemanjai]

Yes, the PowerISA has removed the Book E as of v3.0. @nickdesaulniers can you comment on where this is coming from? We don't have this implemented but if it is needed, we can go ahead with https://reviews.llvm.org/D156204.

[ecnelises]

Landed as 53648ac

Should we backport it to 17.x?

[nickdesaulniers]

Yes, please. We can work around this in the kernel using .inst assembler directives for older versions of clang, but having it sooner would allow us to drop the workaround sooner.

[nickdesaulniers]

oh no, is .inst aarch64-only? :(

EDIT: oh I can use .long here.

[ecnelises]

/cherry-pick 53648ac

[llvmbot]

/cherry-pick 53648ac

Error: Command failed due to missing milestone.

[ecnelises]

/cherry-pick 53648ac